1. Field of the Invention
The present invention relates to a method of manufacturing fiber-reinforced plastics articles, such as construction panels, boat hulls, roof tiles, car body parts, etc; by deep-drawing a planar prepeg comprising fibers impregnated with curable resins; and curing the said resins after deep-drawing of the prepeg. The invention also relates to a method of manufacturing said planar prepegs, and to a mold to be used for said deep-drawing.
2. DESCRIPTION OF THE PRIOR ART
Prepegs consisting of fiber mats which are impregnated by curable resins have been deep-drawn in open contoured mold dies having bore holes, by exerting a subatmospheric pressure, and subsequent UV-light curing, see U.S. Pat. No. 4,478,771 (Schreiber). However, these molds have serious drawbacks since the prepeg is drawn with a relatively great force towards the bore holes but with much weaker forces towards portions remote from those holes. Accordingly, uniform shaping of the web, especially at curved portions of the mold having small radii, will not occur. Vacuum deep-draw molds have also become known. Thus, Japanese patent publication 62-39218 (Kasuga) discloses a vacuum forming mold composed of a mixture of sands and a furan resin. This mold has been designed for the deep-drawing of polypropylene sheets, thus an extensible, thermoplastic material, and it has been found that such molds cannot be used for the deep-drawing of prepregs.
Fiber reinforced prepregs have been prepared by simply soaking of a fiber mat or other fiber arrangement in liquid resins. In order to keep the resin within the fiber mat and prevent it from leaking, the resin must have a relatively high viscosity. However, this very viscosity leads to leaving air bubbles within the mat. This causes a significant loss of strength in the cured prepreg.